Conventionally, as one that detects an object that is approaching from the front or a side of a vehicle of one's own, a vehicle-mounted object detecting device which is mounted on the own-vehicle is known. Specifically, the vehicle-mounted object detecting device detects an object approaching the own-vehicle by means of a radar device (for example, a millimeter wave radar device). Then, based on the detection result, the vehicle-mounted object detecting device determines the risk of a collision between the own-vehicle and the object. In addition, in a case where it is determined that there is a risk of a collision between the own-vehicle and the object, or in other cases, the vehicle-mounted object detecting device controls various devices built into the own-vehicle.
Meanwhile, for an object that exists in the front or a side of the own-vehicle, it is required for the radar device included in the vehicle-mounted object detecting device to accurately acquire information regarding position, azimuth, velocity and the like of the object with regard to the own-vehicle, and to precisely understand the positional relationship between the own-vehicle and the object. Although a radar device included in a general vehicle-mounted object detecting device may recognize an existence of an object, it is often impossible to precisely distinguish the size of the object (for example, a vehicle width of another vehicle). One of such reasons is an inability to enlarge an aperture area of an antenna in the radar device; since, in a case with a radar device that uses radio waves, a resolution of an angle direction is proportional to an aperture area of the antenna. More specifically, since the radar device included in the vehicle-mounted object detecting device is envisioned to be mounted on a vehicle, there are restrictions for the size of the radar device, and the aperture area of the antenna cannot be enlarged.
In addition, generally, in the vehicle-mounted object detecting device, in order to enhance the resolution of the radar device applied in the vehicle-mounted object detecting device, a method is used in which a plurality of reception antenna elements are disposed in the radar device. Additionally, generally, the current situation for the vehicle-mounted object detecting device is that a signal processing method with a high processing load such as DBF (Digital Beam Forming) and MUSIC (MUltiple SIgnal Classification) are applied on signals received from reception antennae in order to compensate for the insufficient resolution. However, on the other hand, for example, a technology disclosed in patent literature 1 is a technology that achieves a radar as if it has an antenna having a large aperture area even with a radar device including a small number of antenna elements.